Spray deposited ruthenium incorporated CdO thin films for opto-electronic and gas sensing applications

The ruthenium (Ru) doped CdO thin films were deposited by spray pyrolysis method on glass substrate, with various Ru concentrations (0.1, 0.125, 0.150, 0.175 and 0.2 wt%). The effect of Ru doping concentration on the electrical, optical, structural, microstructural and gas sensing properties was studied by Hall measurement, UV–vis–NIR spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, micro-Raman and chemi-resistivity method. The results obtained show that the carrier mobility, visible-NIR transparency, surface morphology and gas response are effectively tuned by varying Ru doping concentration. The 0.1 wt% Ru doped CdO thin film shows relatively high optical band gap (2.32 eV) and maximum transmittance (70%) in the range between 600 and 900 nm. The high electrical properties (mobility 110 cm²/V⋅s and carrier concentration 1.77 × 10²⁰ cm⁻³) are obtained for 0.150 wt% Ru doped CdO thin film. The high formaldehyde gas sensitivity (35%), fast response and recovery time are observed for 0.150 wt% Ru doped CdO thin film.